11& MEM0R1AS CIENTIFICAS I LITERARIAS 
X L 2 X d X . 
u=L 2 x du = 2Lx “ X - 
x 
d v = x d x 
v=- 2 -xS 
= “-x 2 L 2 x — J xLxdx. 
= 4- x 2 L 2 X — 4- X 2 L x + 4- X 2 
2 2 4 
5 / e x cos x d x . 
u=cos x 
dv = e x dx 
. . d u = — sen x d x 
v = e x 
/ e x cos x d x = e x cos x +/ e x sen x d x . 
( 1 > 
u = sen x 
d v = e x d x 
. . du = cos x d x 
v = e x 
/ e x sen x d y=e x sen x— / e x cos xdx 
( 2 ) 
De las igualdades (1) i (2), sacamos: 
/ 
e x cos x d x = - - e x (sen x + cos x) 
i 
e x sen x d x = — e x (sen x - cos x) 
£ 
6. / e a x cos b x d x 
u — cos b x . • . du= — senbx.b d x 
, j eax 
dv = e ax dx . y = 
